# Phase 2: Mesh as Federation Transport

## Context

Phase 1 built three independent communication silos: Tor-HTTP for federation, Meshcore LoRa for offline mesh, Nostr relays for discovery. They share no common abstraction — federation hardcodes Tor SOCKS5, mesh has its own serial listener, peer messaging uses a separate HTTP POST. Adding a new transport (LAN/mDNS) or changing routing logic means touching every caller.

Phase 2 unifies these under a `NodeTransport` trait with automatic transport selection per peer (Mesh > LAN > Tor), chunked LoRa messaging with Reed-Solomon FEC for payloads >160 bytes, CBOR delta compression for state sync, mDNS LAN discovery, and a "mesh only" off-grid mode.

The v2.0 roadmap (`docs/roadmap-v2.0.md`) also calls for a visual topology map and CRDT-based state sync — those are deferred to Phase 5 (Mesh Intelligence), but the transport abstraction here enables them.

## Dependencies (Verified)

```toml
ciborium = "0.2.2"            # CBOR serde (134M downloads, active)
reed-solomon-erasure = "6.0"  # FEC (4M downloads, MIT)
mdns-sd = "0.18.2"            # LAN peer discovery (1.86M, active)
```

## Architecture

```
core/archipelago/src/transport/
├── mod.rs              — NodeTransport trait, TransportKind, TransportRouter, PeerRegistry
├── tor.rs              — TorTransport (wraps node_message.rs SOCKS5 logic)
├── mesh_transport.rs   — MeshTransport (bridges MeshService cmd channel)
├── lan.rs              — LanTransport (mdns-sd + direct HTTP)
├── chunking.rs         — Split/reassemble with Reed-Solomon FEC
└── delta.rs            — CBOR delta encoding for NodeStateSnapshot
```

### Unified Peer Identity

DID is the canonical identifier. Transport-specific addresses are attributes:

```rust
pub struct PeerRecord {
    pub did: String,
    pub pubkey_hex: String,
    pub name: Option<String>,
    pub trust_level: TrustLevel,
    // Transport capabilities
    pub mesh_contact_id: Option<u32>,
    pub lan_address: Option<SocketAddr>,
    pub onion_address: Option<String>,
    // Freshness
    pub last_mesh: Option<String>,
    pub last_lan: Option<String>,
    pub last_tor: Option<String>,
}
```

### Transport Routing

```
TransportRouter::send_to_peer(did, payload)
  1. Look up PeerRecord by DID
  2. Filter to transports where peer has address AND transport is available AND not stale
  3. Sort by priority: Mesh(1) > LAN(2) > Tor(3)
  4. If mesh_only_mode: only allow Mesh
  5. Try each in order, fall back on failure
```

### Chunking Protocol (for LoRa >160B)

Per-chunk structure (8 byte header + 124 byte payload = 132B, fits in 160B after encryption):
```
[0x01] [msg_id: u32 LE] [chunk_idx: u8] [total: u8] [is_parity: u8] [payload: 124B]
```

Reed-Solomon: 25% parity shards. 4 data chunks = 1 parity chunk. Any N-of-(N+parity) reconstructs.
Max practical: ~10 chunks (~1.2KB) before LoRa airtime becomes unreasonable.

### CBOR Delta Sync

Full JSON state: ~500-2000 bytes. CBOR delta when only CPU/mem changed: ~30-50 bytes. Fits single LoRa chunk.

```rust
pub struct StateDelta {
    pub ts: String,
    pub v: u8,
    pub apps: Option<Vec<AppStatus>>,      // Only changed apps
    pub apps_rm: Option<Vec<String>>,       // Removed app IDs
    pub cpu: Option<f64>,
    pub mem_u: Option<u64>,
    // ... only changed fields, short names for wire size
}
```

## Implementation Steps

### Step 1: Add deps to Cargo.toml
**File**: `core/archipelago/Cargo.toml`
Add ciborium, reed-solomon-erasure, mdns-sd.

### Step 2: Create `transport/mod.rs` — Core trait + PeerRegistry + TransportRouter
**New file**: `core/archipelago/src/transport/mod.rs`
- `NodeTransport` trait: `kind()`, `is_available()`, `send(address, payload)`
- `TransportKind` enum: `Mesh = 1, Lan = 2, Tor = 3`
- `TransportMessage`: `{from_did, payload: Vec<u8>, message_type}`
- `PeerRegistry`: unified peer store (DID -> PeerRecord), JSON persistence to `transport-peers.json`
- `TransportRouter`: holds Vec<Box<dyn NodeTransport>>, routes by priority with fallback
- Register `mod transport;` in `core/archipelago/src/lib.rs` or main.rs

### Step 3: Create `transport/chunking.rs` — Reed-Solomon FEC
**New file**: `core/archipelago/src/transport/chunking.rs`
- `encode_chunked(data: &[u8]) -> Vec<Vec<u8>>` — split + FEC parity shards
- `ChunkReassembler` — state machine tracking pending messages, attempts reconstruction when enough chunks arrive
- `decode_chunked(chunks: &[Option<Vec<u8>>]) -> Result<Vec<u8>>` — reconstruct from data+parity
- Unit tests: roundtrip, missing chunks, corrupted chunks

### Step 4: Create `transport/delta.rs` — CBOR delta sync
**New file**: `core/archipelago/src/transport/delta.rs`
- `compute_delta(prev, curr: &NodeStateSnapshot) -> StateDelta`
- `apply_delta(base: &NodeStateSnapshot, delta: &StateDelta) -> NodeStateSnapshot`
- `encode_cbor(delta) -> Vec<u8>` via ciborium
- `decode_cbor(bytes) -> Result<StateDelta>`
- Unit tests: delta correctness, CBOR roundtrip, size comparison vs JSON

### Step 5: Create `transport/tor.rs` — TorTransport
**New file**: `core/archipelago/src/transport/tor.rs`
- Wraps existing `node_message::send_to_peer()` pattern (reqwest + SOCKS5)
- Reuses: `node_message.rs:66` send logic, `node_message.rs:115` health check
- `is_available()` checks SOCKS5 proxy reachable at 127.0.0.1:9050
- Receives handled by existing HTTP handler in `api/handler.rs`

### Step 6: Create `transport/mesh_transport.rs` — MeshTransport
**New file**: `core/archipelago/src/transport/mesh_transport.rs`
- Holds reference to `Arc<RwLock<Option<MeshService>>>` (same as RpcHandler)
- `send()` routes through `MeshService::send_message()` for small payloads
- For payloads >124B: chunk with `chunking::encode_chunked()`, send each chunk via `MeshCommand::SendText`
- 200ms inter-chunk delay for LoRa airtime fairness
- `is_available()` checks mesh device connected via `MeshService::status()`

### Step 7: Create `transport/lan.rs` — LanTransport
**New file**: `core/archipelago/src/transport/lan.rs`
- Uses `mdns-sd::ServiceDaemon` for discovery
- Advertises: `_archipelago._tcp.local.` with TXT records: `did=..., pubkey=..., version=...`
- Browses for peers, updates PeerRegistry when found
- `send()`: direct HTTP POST to `http://{ip}:5678/archipelago/node-message` (same endpoint as Tor, no proxy)
- Non-blocking init — if Avahi not available, fail gracefully

### Step 8: Add `mesh_only_mode` to MeshConfig
**File**: `core/archipelago/src/mesh/mod.rs`
- Add `pub mesh_only_mode: Option<bool>` to MeshConfig (with `#[serde(default)]`)
- TransportRouter reads this flag to restrict routing

### Step 9: Wire TransportRouter into server.rs
**File**: `core/archipelago/src/server.rs` (~line 136, after mesh service init)
- Create PeerRegistry, load from disk
- Create TorTransport, MeshTransport, LanTransport
- Start LAN advertisement + discovery
- Create TransportRouter with all three + mesh_only flag
- Spawn background task bridging `MeshEvent::IdentityReceived` -> PeerRegistry
- Store router on RpcHandler

### Step 10: Add transport RPC endpoints
**New file**: `core/archipelago/src/api/rpc/transport.rs`
**Modify**: `core/archipelago/src/api/rpc/mod.rs` (add dispatch routes)

Endpoints:
- `transport.status` — available transports, mesh_only flag, peer count
- `transport.peers` — unified peer list with per-peer transport capabilities + preferred transport
- `transport.send` — send message via best transport (by DID)
- `transport.set-mode` — toggle mesh_only mode

### Step 11: Add opt-in federation sync via transport
**File**: `core/archipelago/src/federation.rs`
- Add `sync_with_peer_via_transport()` alongside existing `sync_with_peer()`
- Uses CBOR delta encoding when transport is mesh (saves bandwidth)
- Falls back to full JSON over Tor for backward compat
- Background sync task checks for TransportRouter, uses it if available

### Step 12: Frontend — transport store + UI indicators
**New file**: `neode-ui/src/stores/transport.ts` — Pinia store for transport status
**Modify**: `neode-ui/src/views/Mesh.vue` — "OFF-GRID" indicator when mesh_only mode
**Modify**: `neode-ui/mock-backend.js` — add transport.* mock RPC responses

### Step 13: Mock backend transport data
**File**: `neode-ui/mock-backend.js`
Add `transport.status`, `transport.peers`, `transport.send`, `transport.set-mode` mock responses with realistic data showing mixed transport capabilities.

## Files Summary

### New (8)
1. `core/archipelago/src/transport/mod.rs`
2. `core/archipelago/src/transport/tor.rs`
3. `core/archipelago/src/transport/mesh_transport.rs`
4. `core/archipelago/src/transport/lan.rs`
5. `core/archipelago/src/transport/chunking.rs`
6. `core/archipelago/src/transport/delta.rs`
7. `core/archipelago/src/api/rpc/transport.rs`
8. `neode-ui/src/stores/transport.ts`

### Modified (8)
1. `core/archipelago/Cargo.toml` — add 3 deps
2. `core/archipelago/src/lib.rs` or main — `mod transport;`
3. `core/archipelago/src/server.rs` — init router, bridge events
4. `core/archipelago/src/api/rpc/mod.rs` — dispatch + store router
5. `core/archipelago/src/mesh/mod.rs` — `mesh_only_mode` config field
6. `core/archipelago/src/federation.rs` — `sync_with_peer_via_transport()`
7. `neode-ui/src/views/Mesh.vue` — off-grid indicator
8. `neode-ui/mock-backend.js` — transport.* mock data

### Reused Existing Code
- `node_message.rs:66-112` — Tor SOCKS5 send logic -> wrapped by TorTransport
- `node_message.rs:115-135` — Tor health check -> TorTransport.is_available()
- `mesh/mod.rs:209-282` — MeshService::send_message() -> called by MeshTransport
- `mesh/listener.rs:35-37` — MeshCommand channel -> used for chunked sends
- `mesh/crypto.rs` — X25519 ECDH + ChaCha20-Poly1305 -> reused as-is
- `federation.rs:36-49` — FederatedNode struct -> PeerRecord wraps this
- `federation.rs:179-191` — update_node_state() -> adapted for CBOR deltas

## Verification

1. **Unit tests** (run on dev server):
   ```bash
   cargo test --all-features -- transport
   cargo test --all-features -- chunking
   cargo test --all-features -- delta
   ```

2. **Frontend type check**:
   ```bash
   cd neode-ui && npm run type-check
   ```

3. **Dev mode test**:
   ```bash
   cd neode-ui && npm start
   # Navigate to /dashboard/mesh — verify OFF-GRID toggle
   ```

4. **Deploy + integration test**:
   ```bash
   ./scripts/deploy-to-target.sh --live
   # On .228: curl transport.status RPC
   # Verify mDNS advertises _archipelago._tcp.local.
   # If mesh device connected: send chunked message >160B to .198
   # Verify federation sync uses CBOR delta when available
   ```

## Implementation Order

**Week 1**: Steps 1-4 (deps, trait, chunking, delta — pure library code with unit tests)
**Week 2**: Steps 5-7 (three transport implementations)
**Week 3**: Steps 8-11 (integration: server wiring, RPC, federation migration)
**Week 4**: Steps 12-13 (frontend UI, mock data, deploy + test)